There are known various different types of multi-hulled water craft. Most twin hulled vessels or catamarans have the two hulls fixed to a common chassis and superstructure (body) or integral with the body, but this generates high stresses in the structure. For example when large waves are encountered head-on and the hulls slam into the waves, without resilient suspension there is a high acceleration transmitted directly to the body or chassis which not only generates high loads through the structure, but also high forces on the occupants with such slamming events causing significant discomfort. Typically the tunnel between the left and right hulls is closed and has its top (the belly of the body) above the water, but during slamming the tunnel can become filled with water generating further high loads into the structure and more jarring inputs to the occupants. If large waves are encountered at an angle, the pitching moments on the left and right hulls can differ greatly, generating high torsional loads and stresses in the structure.
Similarly, most vessels with three hulls (trimarans) have all three hulls fixed to a common chassis or the three hulls and the body are molded and bonded together. Again, slamming of the rigid hulls and reaching the limited capacity of the tunnels between the hulls can induce high accelerations and stresses on the structure, occupants and any cargo of most conventional trimarans where the hulls are fixed and waves encountered at an angle can generate high torsional loads.
In such multi-hulled vessels it is known to provide a torsionally resilient chassis to absorb some of the wave energy and reduce the loading and corresponding weight of the chassis. It has alternatively been proposed to provide resilient suspension in the form of individual coil springs between the hulls and the chassis. While this arrangement adds resilient suspension between the side hulls and the body or chassis, it has the disadvantage that it provides the same fixed stiffness in each suspension mode (roll, pitch, heave and warp), so any reduction in the warp stiffness to reduce torsional loading into the body results in a corresponding reduction in roll, pitch and heave stiffness.